mypasswordis Posted March 2, 2011 Report Posted March 2, 2011 Kind of a random place to ask this, but I want to build the Jecklin 'stat amp at some point. I have a whole bunch of mixed 12AU7/A tubes but no idea how to tell what is what. Eventually I'll have to invest in a tube tester for matching but does anyone have a link to some reference that lists the defining features of various 12AU7s? Might have to buy another mixed lot of 12AU7s to actually find some that are same internally and match...
Pars Posted March 2, 2011 Report Posted March 2, 2011 I don't know how much this lists in terms of internal construction, but might be of some help: Joe's tube lore
mypasswordis Posted March 2, 2011 Report Posted March 2, 2011 Thanks, that's a start. The thing is I have 20 or so tubes and iirc ~15 of them have different labels so I'm trying to find the ones that are the same internally or if they are all different. I'll go through the list and sort the tubes when I get home. Here's a crappy ebay pic of a production unit:
padam Posted March 2, 2011 Report Posted March 2, 2011 Anybody saw this design? Looks pretty simple. (guy also built a DIY T2) http://d.hatena.ne.jp/inuponken/20100806/1281052930
livewire Posted March 2, 2011 Report Posted March 2, 2011 Got any pix of the underside(s)? Gerbers would be better!
DouglasQuaid Posted March 2, 2011 Report Posted March 2, 2011 Are my eyes deceiving me or are those actually black solder pads?
livewire Posted March 2, 2011 Report Posted March 2, 2011 Green solder mask over black pcb substrate maybe?
livewire Posted March 2, 2011 Report Posted March 2, 2011 (edited) They are Headamp boards, maybe Justin or one those who have bought these boards from him could answer that. Once upon a time I tried to procure these, but never received an answer to my request. Gee, how odd... Edited March 3, 2011 by livewire
kevin gilmore Posted March 3, 2011 Report Posted March 3, 2011 Not a black circuit board. just reflections from the scanner or camera from the solder mask.
spritzer Posted March 3, 2011 Author Report Posted March 3, 2011 Just like Kevin said, these are just normal green boards. Got any pix of the underside(s)? Gerbers would be better! These are from Headamp so no pics of the underside. As for the Gerber's... yeah good luck with that...
Antistar Posted March 8, 2011 Report Posted March 8, 2011 Very cool bringing back them pics sptizer, kodus señor So i own a DIY KGSS (not by myself) and was suggested the 17N80C3 for replacing the N-channel Mosfets at the PS section after previous repeated failings of one the IRF830 that was there...though i'm not techwise i think it's the one who handles the +350V, beacuse it's dropped almost flat. Is it a better fit? I see it's very pricey compared to IRF830, Is there some other decent alternative on a budget?
kevin gilmore Posted March 8, 2011 Report Posted March 8, 2011 Depends on which version of the power supply board you have, but 24 volt zeners across the gate to source prevents the pass transistor from blowing up. The fairchild part used in the T2 is way better anyway.FQPF8N80C or FQP8N80C and they are cheap. Probably still out of stock at mouser, so get them at futureelectronics.
DouglasQuaid Posted March 8, 2011 Report Posted March 8, 2011 Speaking of the KGSS/KGBH supply boards, how long do they need to sit after testing before they are safe to handle, assuming they are sitting with the outputs entirely unloaded.
livewire Posted March 8, 2011 Report Posted March 8, 2011 I can only speak regarding the KGSSHV board that I have built. I'm assuming that others would be similar depending on if they have bleeder resistors across the supplies filter capacitors. Also bleeddown time is governed by the cap's size (in mfd's) and the size of the bleeder resistor. I'm sure there is a mathematical formula that describes this, but I dont know it. The best way (for me) to be sure is to use a voltmeter to read the remaining voltage charge across the filter capactiors on the psu when switched off. For a given power supply, I use a stopwatch and check the caps multiple times until they bleed down to a "safe" voltage, say a couple of volts DC. Make sure that the thing is unplugged before starting and remember that the voltages encountered here are deadly! If you become part of the circuit, it can stop your heart, that is cause fibrillation that may result in death. My KGSSHV supply bleeds down to a safe level in about a minute. The specified bleeder resistors for this psu are 300K ohms to 400K ohm units. The intial voltage on each rail is 450 volts DC, so it has a total potential of double that, or 900 volts DC.
DouglasQuaid Posted March 8, 2011 Report Posted March 8, 2011 I was definitely going to check with a dmm before handling, but I didn't want to set up the psu here at the lab and have to stick around for an hour before things were safe to handle. 400V is the most I've worked with here at the lab so far, and it was more than enough to kill me at the currents I was working at. I'll definitely be keeping track of anything I touch. My plan is to use two DMMs, one on the positive rail and one on the negative rail, and attach probes before turning the psu on so I don't have to worry about exposing myself to the HV supplies.
livewire Posted March 8, 2011 Report Posted March 8, 2011 Also keep in mind that a power supply that does not utilize bleeder resistors that are connected across the filter capacitors can harbor a deadly charge for days even when unplugged. Think of the filter capacitors as high voltage batteries. Be very careful!
Antistar Posted March 8, 2011 Report Posted March 8, 2011 Depends on which version of the power supply board you have, but 24 volt zeners across the gate to source prevents the pass transistor from blowing up. The fairchild part used in the T2 is way better anyway.FQPF8N80C or FQP8N80C and they are cheap. Probably still out of stock at mouser, so get them at futureelectronics. I don't have the amp to check the board version currently but that's exactly what happend the second time, the IRF830 actually blew apart to pieces, and the fuze got whacked too. I'll check those T2 parts, thanks. Couldn't be any worse i guess ... heh.
livewire Posted March 8, 2011 Report Posted March 8, 2011 (edited) @DQ, Some may think this is excessive, when I work with high voltages like this I have a ground strap attached to each arm and the device under test and perform the work while using a nonconductive rubber mat underfoot & on the workbench. I make a lot of mistakes, like slipping with the test probes, some of which are chronicled here on HC. I dont want a multi-hundred volt charge crossing through my heart, if you get my drift. On the job as a maintenance electrician, I have been shocked many times. Using safety procedures like these has probably saved my bacon numerous times. Edited March 8, 2011 by livewire
livewire Posted March 8, 2011 Report Posted March 8, 2011 I was definitely going to check with a dmm before handling, but I didn't want to set up the psu here at the lab and have to stick around for an hour before things were safe to handle. 400V is the most I've worked with here at the lab so far, and it was more than enough to kill me at the currents I was working at. I'll definitely be keeping track of anything I touch. My plan is to use two DMMs, one on the positive rail and one on the negative rail, and attach probes before turning the psu on so I don't have to worry about exposing myself to the HV supplies. That is a good idea, keep in mind that if the psu does not utilize bleeder resistors, your DMM will act as one due to it's internal (high) impedance. The bleed-off time if noted, will only be valid for bleed down with that meter attached. At least you will know when it has become discharged and be safe to handle.
kevin gilmore Posted March 8, 2011 Report Posted March 8, 2011 (edited) inu sent me these which are variations on the srx circuit. http://earsp.web.fc2.com/log/stax-r/stax-r-3.pdf warning, the 1150 volt version is only for those that really know what they are doing. And obviously the output caps need to be rated for 1200 or more volts. With respect to high voltage electrolytics, and also mylar caps, a resistor across the cap is pretty much required at all times. Even if you discharge the cap, and then remove the resistor, the capacitor will self charge, usually to very dangerous voltages. The higher the rating on the cap, the worse it gets. Edited March 8, 2011 by kevin gilmore
livewire Posted March 8, 2011 Report Posted March 8, 2011 inu sent me these which are variations on the srx circuit. http://earsp.web.fc2.com/log/stax-r/stax-r-3.pdf warning, the 1150 volt version is only for those that really know what they are doing. And obviously the output caps need to be rated for 1200 or more volts. With respect to high voltage electrolytics, and also mylar caps, a resistor across the cap is pretty much required at all times. Even if you discharge the cap, and then remove the resistor, the capacitor will self charge, usually to very dangerous voltages. The higher the rating on the cap, the worse it gets. Words of wisdom! (regarding the caps) Can anybody here translate the japanese? I'm sure just viewing the schemos is all KG needs to see. Rest assured, I wont be messing with any of that HV tube stuff.
kevin gilmore Posted March 9, 2011 Report Posted March 9, 2011 i'm sure inu could translate it. but i know a couple of people at work that can do it too. maybe in the next few days. really, these things are just the srx circuit with an extra tube stage for more gain so that you can have more feedback. 50ca10's are probably impossible to get, as are the sockets, 6ra9's might be easier. Still nothing wrong with 6ca7's. But the resistor plate loads are guaranteed to do the same thing that has happened to a bunch of the es1/es2's when the output tube lets go. So much better idea to replace with current source. Then make sure you have adjustable bias on the output tube. Pretty soon you end up with the modified singlepower schematic. There are errors in the schematics, in the 3rd one, "B" is actually -440 volts. With the 50c10's you can do adjustable self bias without an additional negative power supply.
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